CYG X-3 IN ITS LOW STATE

ABSTRACT

In the low state of Cyg X-3, it shows the brightest iron emission line in the sky. ASCA, however, has not yet observed the low state of Cyg X-3. Cyg X-3 was observed with ASCA two times in its high state. ASCA found many emission lines form various elements and emission-line-like feature produced by free-bound transition for S XVI. This was the first direct evidence of the photo-ionized plasma in the universe. The plasma condition should be influenced by the luminosity and the energy spectrum of the central source. The observation of the low state of Cyg X-3 will provide various surprising feature that we have never seen.